PJM Weighs New Surplus Interconnection Path to Bring Batteries and Generation Online Faster

PJM Interconnection is considering another change to its surplus interconnection process after stakeholders raised a proposal this week aimed at making unused grid-connection rights at existing power plants easier for new generation and battery-storage projects to access. The PJM surplus interconnection discussion matters across the 13-state regional grid because developers may be able to bring capacity online faster by using existing interconnection infrastructure instead of entering the full generation queue.

The existing surplus pathway has attracted relatively little development in PJM even as neighboring grid operators study gigawatts of projects using similar mechanisms. PJM’s current rules already allow surplus projects to use the unused portion of an existing facility’s interconnection service as long as total interconnection service at the point of connection does not increase.

The proposal focuses on interconnection capacity that already exists

PJM defines a surplus interconnection request as a generation project using an unused portion of an existing generating facility’s interconnection service while keeping the total amount of service at the point of interconnection unchanged.

That creates a potential alternative to building an entirely new grid connection. For example, a battery could be added at a power facility whose interconnection rights are not fully used during every operating hour.

The concept can be particularly useful for resources with complementary operating profiles. A solar facility, for example, may not use its full interconnection capability at night, while a co-located battery can charge or discharge at different times without necessarily increasing the maximum amount of power flowing through the grid connection.

PJM has previously highlighted adding battery storage to solar generation as an example of how surplus interconnection service can make better use of existing grid infrastructure.

Earlier PJM reforms broadened eligibility

The current PJM surplus interconnection debate follows reforms that became effective in March 2025.

PJM’s manual-update record shows that those changes allowed developers to request surplus service from planned as well as existing generating facilities and removed certain restrictions involving network-upgrade determinations and system impacts.

The Federal Energy Regulatory Commission accepted those tariff revisions in February 2025, and PJM implemented them the following month.

Despite the changes, the pathway has remained relatively lightly used compared with the scale of projects being evaluated elsewhere. That has prompted another look at whether PJM can make the mechanism easier to use while maintaining reliability safeguards.

Surplus projects still require a PJM study

The process does not allow developers to attach new generation to the transmission system without technical review.

PJM’s Open Access Transmission Tariff requires a Surplus Interconnection Study after the grid operator receives a valid study agreement and the required deposit.

PJM’s current application structure requires a study deposit of $10,000 plus $100 for each megawatt requested, capped at $110,000 for a surplus interconnection request.

Developers also must establish rights to use the existing facility’s interconnection capability. PJM tariff documents require permission from the owner of the existing generating facility when the surplus developer is not the same owner or an affiliate, along with arrangements governing shared facilities.

The pathway could be particularly relevant to battery storage

Battery projects can be well suited to surplus interconnection because their charging and discharging schedules can be coordinated with an existing generator’s output.

Instead of treating the battery and original generating facility as two resources each requiring the full nameplate capacity of a new grid connection, developers can potentially design the combination around the maximum interconnection capacity already available at the site.

That can reduce the need for some network upgrades, but it does not mean every existing power plant has usable surplus capacity. PJM still evaluates whether the proposed resource can operate without creating unacceptable thermal, voltage, short-circuit or stability impacts.

The approach is one of several strategies grid operators are considering as long interconnection queues and rapid electricity-demand growth increase pressure to bring new resources online faster.

PJM is trying to accelerate generation additions

PJM serves a region experiencing substantial growth in electricity demand, including new data centers and other large loads.

The grid operator has been reforming its generation interconnection process while attempting to clear a large historical project backlog. Earlier this month, PJM said more than 700 projects representing over 200 GW had qualified for study in the first cycle of its reformed interconnection process.

Surplus interconnection is different from the main cycle process because it attempts to use transmission access already assigned to an existing or planned facility rather than creating an entirely new interconnection position.

PJM’s application materials currently route surplus requests through its QueuePoint system while its newer NextGen platform handles several other categories of interconnection requests.

What happens next

The latest proposal remains under consideration rather than an adopted tariff change. Any material revision to PJM’s surplus interconnection rules would need to proceed through the stakeholder process and, where tariff revisions are required, receive Federal Energy Regulatory Commission approval.

The policy question is whether PJM can increase utilization of existing grid connections without allowing new projects to impose reliability problems or costs that would otherwise have been identified through the standard interconnection process.

If a workable reform emerges, batteries, renewable generators and other resources located near existing power facilities could gain another route for reaching commercial operation without waiting for a completely new transmission interconnection.

Microgrid Media Editorial Desk

The Microgrid Media Editorial Desk reports on microgrids, energy storage, grid modernization, data center power demand, distributed energy resources, and energy policy. Reporting published under the Editorial Desk byline is developed from primary regulatory records, utility filings, government documents, company disclosures, and independently verifiable sources, and is reviewed under Microgrid Media’s editorial standards.

Editorial oversight: Jonas Muthoni, Editor-in-Chief